Coated detergent tablet

ABSTRACT

The present invention relates to tablets comprising a core and a coating, the core being formed by compressing a particulate material, the particulate material comprising surfactant and detergent builder, and the tablet further comprising a disintegrant, at least some of the disintegrant being in the coating. The invention also relates to processes for making the tablets.

The present invention relates to coated detergent tablets, especiallythose adapted for use in washing machines, and to processes for makingthe coated detergent tablets.

Although cleaning compositions in tablet form have often been proposed,these have not (with the exception of soap bars for personal washing)gained any substantial success, despite the several advantages ofproducts in a unit dispensing form. One of the reasons for this may bethat detergent tablets require a relatively complex manufacturingprocess. In particular, it is often desirable to provide the tablet witha coating and this adds to the difficulties of manufacture.

While tablets without a coating are entirely effective in use, theyusually lack the necessary surface hardness to withstand the abrasionthat is a part of normal manufacture, packaging and handling. The resultis that uncoated tablets suffer from abrasion during these processes,resulting in chipped tablets and loss of active material.

Finally, coating of tablets is often desired for aesthetic reasons, toimprove the outer appearance of the tablet or to achieve some particularaesthetic effect.

Numerous methods of tablet coating have been proposed, and many of thesehave been suggested for detergent tablets. However, all of these methodshave certain disadvantages, as will be explained below.

GB-A-0 989 683, published on Apr. 22, 1965, discloses a process forpreparing a particulate detergent from surfactants and inorganic salts;spraying on water-soluble silicate; and pressing the detergent particlesinto a solid form-retaining tablet. Finally a readily water-solubleorganic film-forming polymer (for example, polyvinyl alcohol) provides acoating to make the detergent tablet resistant to abrasion andaccidental breakage.

EP-A-0 002 293, published on Jun. 13, 1979, discloses a tablet coatingcomprising hydrated salt such as acetate, metaborate, orthophosphate,tartrate, and sulphate.

EP-A-0 716 144, published on Jun. 12, 1996, also discloses laundrydetergent tablets with water-soluble coatings which may be organicpolymers including acrylic/maleic co-polymer, polyethylene glycol,PVPVA, and sugar.

WO9518215, published on Jul. 6, 1995, provides water-insoluble coatingsfor solid cast tablets. The tablets are provided with hydrophobiccoatings including wax, fatty acid, fatty acid amides, and polyethyleneglycol.

A disadvantage of the prior art disclosures is that a coating which isthick enough and strong enough to withstand abrasion, also tends to beslow to break up or dissolve in use.

The present invention provides a means by which tablets with a corewhich is formed by compressing a particulate material, the particulatematerial comprising surfactant and detergent builder, can be providedwith a hard, thin, coating so that they can be stored, shipped andhandled, but the coating is broken when the tablet is in the washingmachine exposing the soft core which breaks up easily and rapidly,releasing the active ingredients into the wash solution.

The objective of the present invention is to provide a tablet whichcompletely disintegrates and disperses, in particular in alkaline orsurfactant-rich solutions such as the wash liquor.

SUMMARY OF THE INVENTION

The object of the present invention is achieved by providing a tabletwhich further comprises a disintegrant, at least some of thedisintegrant being in the coating. It is preferred that the tabletfurther comprises an effervescent, for example a soluble acid source andan alkali metal carbonate.

In a further aspect of the invention there is provided a process formaking a tablet comprising the steps of:

(a) forming a core by compressing a particulate material, theparticulate material comprising surfactant and detergent builder;

(b) applying a coating material to the core, the coating material beingin the form of a melt;

(c) allowing the molten coating material to solidify;

wherein the coating material comprises a disintegrant. Preferably thecoating materials have a melting point in the range of from 40° C. to200° C.

In an alternative to this embodiment of the invention there is provideda process for making a tablet comprising the steps of:

(a) forming a core by compressing a particulate material, theparticulate material comprising surfactant and detergent builder;

(b) applying a coating material to the core, the coating material beingdissolved in a solvent;

(c) allowing the solvent to evaporate;

wherein the coating material comprises a disintegrant.

DETAILED DESCRIPTION OF THE INVENTION

Tablets to be coated in the present invention can be prepared simply bymixing the solid ingredients together and compressing the mixture in aconventional tablet press as used, for example, in the pharmaceuticalindustry. Any liquid ingredients, for example the surfactant or sudssuppressor, can be incorporated in a conventional manner into the solidparticulate ingredients. Preferably the principal ingredients, are usedin particulate form.

In particular for laundry tablets, the ingredients such as builder andsurfactant can be spray-dried in a conventional manner and thencompacted at a suitable pressure. The detergent tablets can be made inany size or shape and can, if desired, be surface treated beforecoating, according to the present invention. In the core of the tabletis included a surfactant and a builder which normally provides asubstantial part of the cleaning power of the tablet. The term “builder”is intended to mean all materials which tend to remove calcium ion fromsolution, either by ion exchange, complexation, sequestration orprecipitation.

The particulate material used for making the tablet of this inventioncan be made by any particulation or granulation process. An example ofsuch a process is spray drying (in a co-current or counter current spraydrying tower) which typically gives low bulk densities 600 g/l or lower.Particulate materials of higher density can be prepared by granulationand densification in a high shear batch mixer/granulator or by acontinuous granulation and densification process (e.g. using Lodige® CBand/or Lodige® KM mixers). Other suitable processes include fluid bedprocesses, compaction processes (e.g. roll compaction), extrusion, aswell as any particulate material made by any chemical process likeflocculation, crystallisation sentering, etc. Individual particles canalso be any other particle, granule, sphere or grain.

The particulate materials may be mixed together by any conventionalmeans. Batch is suitable in, for example, a concrete mixer, Nauta mixer,ribbon mixer or any other. Alternatively the mixing process may becarried out continuously by metering each component by weight on to amoving belt, and blending them in one or more drum(s) or mixer(s). Aliquid spray-on to the mix of particulate materials (e.g. non-ionicsurfactants) may be carried out. Other liquid ingredients may also besprayed on to the mix of particulate materials either separately orpremixed. For example perfume and slurries of optical brighteners may besprayed. A finely divided flow aid (dusting agent such as zeolites,carbonates, silicas) can be added to the particulate materials afterspraying the non-ionic, preferably towards the end of the process, tomake the mix less sticky.

The tablets may be manufactured by using any compacting process, such astabletting, briquetting, or extrusion, preferably tabletting. Suitableequipment includes a standard single stroke or a rotary press (such asCourtoy®, Korch®, Manesty®, or Bonals®. The tablets prepared accordingto this invention preferably have a diameter of between 40 mm and 50 mm,and a weight between 25 and 60 g. The compaction pressure used forpreparing these tablets need not exceed 5000 kN/m², preferably notexceed 3000 kN/m², and most preferably not exceed 1000 kN/m².

According to the present invention, the tablets are then coated with acoating so that the tablet does not absorb moisture, or absorbs moistureat only a very slow rate. The coating is also strong so that moderatemechanical shocks to which the tablets are subjected during handling,packing and shipping result in no more than very low levels of breakageor attrition. Finally the coating is preferably brittle so that thetablet breaks up when subjected to stronger mechanical shock.Furthermore it is advantageous if the coating material is dissolvedunder alkaline conditions, or is readily emulsified by surfactants. Thisavoids the deposition of undissolved particles or lumps of coatingmaterial on the laundry load. This may be important when the coatingmaterial is completely insoluble (for example less than 1 g/l) in water.

As defined herein “substantially insoluble” means having a very lowsolubility in water. This should be understood to mean having asolubility in water at 25° C. of less than 20 g/L, preferably less than5 g/l, and more preferably less than 1 g/l. Water solubility is measuredfollowing the test protocol of ASTM E1148-87 entitled, “Standard TestMethod for Measurements of Aqueous Solubility”.

Suitable coating materials are fatty acids, C₂-C₁₃ dicarboxylic acids,fatty alcohols, diols, esters and ethers. Preferred fatty acids arethose having a carbon chain length of from C12 to C22 and mostpreferably from C18 to C22. Preferred dicarboxylic acids are oxalic acid(C2), malonic acid (C3), succinic acid (C4), glutaric acid (C5), adipicacid (C6), pimelic acid (C7), suberic acid (C8), azelaic acid (C9),sebacic acid (C10), undecanedioic acid (C11), dodecanedioic acid (C12)and tridecanedioic acid (C13). Preferred fatty alcohols are those havinga carbon chain length of from C12 to C22 and most preferably from C14 toC18. Preferred diols are 1,2-octadecanediol and 1,2-hexadecanediol.Preferred esters are tristearin, tripalmitin, methylbehenate,ethylstearate. Preferred ethers are diethyleneglycol monohexadecylether, diethyleneglycol mono octadecylether, diethyleneglycolmono Otetradecylether, phenylether, ethyl naphtyl ether, 2methoxynaphtalene, betanaphtyl methyl ether and glycerolmonooctadecylether. Other preferred coating materials include dimethyl2,2 propanol, 2 hexadecanol, 2 octadecanone, 2 hexadecanone, 2, 15hexadecanedione and 2 hydroxybenzyl alcohol.

However the detergent tablets are prepared and in whatever from theyare, they are then coated according to the present invention with acoating material having a melting point preferably of from 40° C. to200° C.

The coating can be applied in a number of ways. Two preferred coatingmethods are a) coating with a molten material and b) coating with asolution of the material.

In a), the coating material is applied at a temperature above itsmelting point, and solidifies on the tablet. In b), the coating isapplied as a solution, the solvent being dried to leave a coherentcoating. The substantially insoluble material can be applied to thetablet by, for example, spraying or dipping. Normally when the moltenmaterial is sprayed on to the tablet, it will rapidly solidify to form acoherent coating. When tablets are dipped into the molten material andthen removed, the rapid cooling again causes rapid solidification of thecoating material. Clearly substantially insoluble materials having amelting point below 40° C. are not sufficiently solid at ambienttemperatures and it has been found that materials having a melting pointabove about 200° C. are not practicable to use. Preferably, thematerials melt in the range from 60° C. to 160° C., more preferably from70° C. to 120° C.

By “melting point” is meant the temperature at which the material whenheated slowly in, for example, a capillary tube becomes a clear liquid.

A coating of any desired thickness can be applied according to thepresent invention. For most purposes, the coating forms from 1% to 10%,preferably from 1.5% to 5%, of the tablet weight.

The tablet coatings of the present invention are very hard and provideextra strength to the tablet.

In the present invention the fracture of the coating in the wash isimproved by adding a disintegrant in the coating. This disintegrant willswell once in contact with water and break the coating in small pieces.This will improve the dissolution of the coating in the wash solution.The disintegrant is suspended in the coating melt at a level of up to30%, preferably between 5 and 20%, and most preferably between 5 and 10%by weight.

Possible disintegrants are described in Handbook of PharmaceuticalExcipients (1986). Examples of suitable disintegrants include starch:natural, modified or pregelatinized starch, sodium starch gluconate;gum: agar gum, guar gum, locust bean gum, karaya gum, pectin gum,tragacanth gum; croscarmylose Sodium, crospovidone, cellulose,carboxymethyl cellulose, algenic acid and its salts including sodiumalginate, silicone dioxide, clay, polyvinylpyrrolidone, soypolysacharides, ion exchange resins and mixtures thereof

Depending on the composition of the starting material, and the shape ofthe tablets, the used compaction force will be adjusted to not affectthe strength (Diametral Fracture Stress), and the disintegration time inthe washing machine. This process may be used to prepare homogenous orlayered tablets of any size or shape.

Diametrical Fracture Stress (DFS) is a way to express the strength of atablet, it is determined by the following equation:$= \frac{2F}{\mu \quad {Dt}}$

Where F is the maximum force (Newton) to cause tensile failure(fracture) measured by a VK 200 tablet hardness tester supplied by VanKell industries, Inc. D is the diameter of the tablet, and t thethickness of the tablet.

(Method Pharmaceutical Dosage Forms: Tablets Volume 2 Page 213 to 217)

The rate of disintegration of a detergent tablet can be determined intwo ways:

a) In a “VAN KEL” Friabilator with “Vankel Type” drums.

Put 2 tablets with a known weight and D.F.S in the Friabilator drum.

Rotate the drum for 20 rotations.

Collect all product and remaining tablet pieces from the Friabilatordrum, and screen it on 5 mm, and through 1.7 mm

Express as % residue on 5 mm and through 1.7 mm.

The higher the % of material through 1.7 mm the better thedisintegration.

b) In a washing machine according to the following method

Take two tablets with a known weight and fracture stress, and put themat the bottom of a washing machine (i.e. a Bauknecht WA 950).

Put a 3 kg mixed load on top of the tablets.

Run a 30° C. short cycle (program 4) with city water.

Stop the cycle after 5 min and check the wash load for undissolvedtablet pieces, collect and weigh them, and record the percent residueleft.

In another preferred embodiment of the present invention the tabletsfurther comprises an effervescent.

Effervescency as defined herein means the evolution of bubbles of gasfrom a liquid, as the result of a chemical reaction between a solubleacid source and an alkali metal carbonate, to produce carbon dioxidegas,

i.e. C₆H₈O₇+3NaHCO₃→Na₃C₆H₅O₇+3CO₂↑+3H₂O

Further examples of acid and carbonate sources and other effervescentsystems may be found in: (Pharmaceutical Dosage Forms: Tablets Volume 1Page 287 to 291)

An effervescent may be added to the tablet mix in addition to thedetergent ingredients. The addition of this effervescent to thedetergent tablet improves the disintegration time of the tablet. Theamount will preferably be between 5 and 20% and most preferably between10 and 20% by weight of the tablet. Preferably the effervescent shouldbe added as an agglomerate of the different particles or as a compact,and not as separated particles.

Due to the gas created by the effervescency in the tablet, the tabletcan have a higher D.F.S. and still have the same disintegration time asa tablet without effervescency. When the D.F.S. of the tablet witheffervescency is kept the same as a tablet without, the disintegrationof the tablet with effervescency will be faster.

Detersive surfactants

Nonlimiting examples of surfactants useful herein typically at levelsfrom about 1% to about 55%, by weight, include the conventional C₁₁-C₁₈alkyl benzene sulfonates (“LAS”) and primary, branched-chain and randomC₁₀-C₂₀ alkyl sulfates (“AS”), the C₁₀-C₁₈ secondary (2,3) alkylsulfates of the formula CH₃(CH₂)_(x)(CHOSO³⁻M⁺) CH₃ and CH₃(CH₂)_(y)(CHOSO³⁻M⁺) CH₂CH₃ where x and (y+1) are integers of at leastabout 7, preferably at least about 9, and M is a water-solubilizingcation, especially sodium, unsaturated sulfates such as oleyl sulfate,the C₁₀-C₁₈ alkyl alkoxy sulfates (“AE_(x)S”; especially EO 1-7 ethoxysulfates), C₁₀-C₁₈ alkyl alkoxy carboxylates (especially the EO 1-5ethoxycarboxylates), the C₁₀₋₁₈ glycerol ethers, the C₁₀-C18 alkylpolyglycosides and their corresponding sulfated polyglycosides, andC₁₂-C₁₈ alpha-sulfonated fatty acid esters. If desired, the conventionalnonionic and amphoteric surfactants such as the C₁₂-C₁₈ alkylethoxylates (“AE”) including the so-called narrow peaked alkylethoxylates and C₆-C₁₂ alkyl phenol alkoxylates (especially ethoxylatesand mixed ethoxy/propoxy), C₁₂-C₁₈ betaines and sulfobetaines(“sultaines”), C₁₀-C₁₈ amine oxides, and the like, can also be includedin the overall compositions. The C₁₀-C₁₈ N-alkyl polyhydroxy fatty acidamides can also be used. Typical examples include the C₁₂-C₁₈N-methylglucamides. See WO 9,206,154. Other sugar-derived surfactantsinclude the N-alkoxy polyhydroxy fatty acid amides, such as C₁₀-C₁₈N-(3-methoxypropyl) glucamide. The N-propyl through N-hexyl C₁₂-C₁₈glucamides can be used for low sudsing. C₁₀-C₂₀ conventional soaps mayalso be used. If high sudsing is desired, the branched-chain C₁₀-C₁₆soaps may be used. Mixtures of anionic and nonionic surfactants areespecially useful. Other conventional useful surfactants are listed instandard texts.

Builders

Detergent builders can optionally be included in the compositions hereinto assist in controlling mineral hardness. Inorganic as well as organicbuilders can be used. Builders are typically used in fabric launderingcompositions to assist in the removal of particulate soils.

The level of builder can vary widely depending upon the end use of thecomposition. Inorganic or P-containing detergent builders include, butare not limited to, the alkali metal, ammonium and alkanolammonium saltsof polyphosphates (exemplified by the tripolyphosphates, pyrophosphates,and glassy polymeric meta-phosphates), phosphonates, phytic acid,silicates, carbonates (including bicarbonates and sesquicarbonates),sulphates, and aluminosilicates. However, non-phosphate builders arerequired in some locales. Importantly, the compositions herein functionsurprisingly well even in the presence of the so-called “weak” builders(as compared with phosphates) such as citrate, or in the so-called“underbuilt” situation that may occur with zeolite or layered silicatebuilders.

Examples of silicate builders are the alkali metal silicates,particularly those having a SiO₂:Na₂O ratio in the range 1.6:1 to 3.2:1and layered silicates, such as the layered sodium silicates described inU.S. Pat. No. 4,664,839, issued May 12, 1987 to H. P. Rieck. NaSKS-6 isthe trademark for a crystalline layered silicate marketed by Hoechst(commonly abbreviated herein as “SKS-6”). Unlike zeolite builders, theNa SKS-6 silicate builder does not contain aluminum. NaSKS-6 has thedelta-Na₂SiO₅ morphology form of layered silicate. It can be prepared bymethods such as those described in German DE-A-3,417,649 andDE-A-3,742,043. SKS-6 is a highly preferred layered silicate for useherein, but other such layered silicates, such as those having thegeneral formula NaMSi_(x)O_(2x+1).yH₂O wherein M is sodium or hydrogen,x is a number from 1.9 to 4, preferably 2, and y is a number from 0 to20, preferably 0 can be used herein. Various other layered silicatesfrom Hoechst include NaSKS-5, NaSKS-7 and NaSKS-11, as the alpha, betaand gamma forms. As noted above, the delta-Na₂SiO₅ (NaSKS-6 form) ismost preferred for use herein. Other silicates may also be useful suchas for example magnesium silicate, which can serve as a crispening agentin granular formulations, as a stabilizing agent for oxygen bleaches,and as a component of suds control systems.

Examples of carbonate builders are the alkaline earth and alkali metalcarbonates as disclosed in German Patent Application No. 2,321,001published on Nov. 15, 1973.

Aluminosilicate builders are useful in the present invention.Aluminosilicate builders are of great importance in most currentlymarketed heavy duty granular detergent compositions, and can also be asignificant builder ingredient in liquid detergent formulations.Aluminosilicate builders include those having the empirical formula:

M_(z)(zAlO₂)_(y) ].xH₂O

wherein z and y are integers of at least 6, the molar ratio of z to y isin the range from 1.0 to about 0.5, and x is an integer from about 15 toabout 264.

Useful aluminosilicate ion exchange materials are commerciallyavailable. These aluminosilicates can be crystalline or amorphous instructure and can be naturally-occurring aluminosilicates orsynthetically derived. A method for producing aluminosilicate ionexchange materials is disclosed in U.S. Pat. No. 3,985,669, Krummel, etal, issued Oct. 12, 1976. Preferred synthetic crystallinealuminosilicate ion exchange materials useful herein are available underthe designations Zeolite A, Zeolite P (B), Zeolite MAP and Zeolite X. Inan especially preferred embodiment, the crystalline aluminosilicate ionexchange material has the formula:

Na₁₂[(AlO₂)₁₂(SiO₂)₁₂ ].xH₂O

wherein x is from about 20 to about 30, especially about 27. Thismaterial is known as Zeolite A. Dehydrated zeolites (x=0-10) may also beused herein. Preferably, the aluminosilicate has a particle size ofabout 0.1-10 microns in diameter.

Organic detergent builders suitable for the purposes of the presentinvention include, but are not restricted to, a wide variety ofpolycarboxylate compounds. As used herein, “polycarboxylate” refers tocompounds having a plurality of carboxylate groups, preferably at least3 carboxylates. Polycarboxylate builder can generally be added to thecomposition in acid form, but can also be added in the form of aneutralized salt. When utilized in salt form, alkali metals, such assodium, potassium, and lithium, or alkanolammonium salts are preferred.

Included among the polycarboxylate builders are a variety of categoriesof useful materials. One important category of polycarboxylate buildersencompasses the ether polycarboxylates, including oxydisuccinate, asdisclosed in Berg, U.S. Pat. No. 3,128,287, issued Apr. 7, 1964, andLamberti et al, U.S. Pat. No. 3,635,830, issued Jan. 18, 1972. See also“TMS/TDS” builders of U.S. Pat. No. 4,663,071, issued to Bush et al, onMay 5, 1987. Suitable ether polycarboxylates also include cycliccompounds, particularly alicyclic compounds, such as those described inU.S. Pat. Nos. 3,923,679; 3,835,163; 4,158,635; 4,120,874 and 4,102,903.

Other useful detergency builders include the etherhydroxypolycarboxylates, copolymers of maleic anhydride with ethylene orvinyl methyl ether, 1,3,5-trihydroxy benzene-2,4,6-trisulphonic acid,and carboxymethyloxysuccinic acid, the various alkali metal, ammoniumand substituted ammonium salts of polyacetic acids such asethylenediamine tetraacetic acid and nitrilotriacetic acid, as well aspolycarboxylates such as mellitic acid, succinic acid, oxydisuccinicacid, polymaleic acid, benzene 1,3,5-tricarboxylic acid,carboxymethyloxysuccinic acid, and soluble salts thereof.

Citrate builders, e.g., citric acid and soluble salts thereof(particularly sodium salt), are polycarboxylate builders of particularimportance for heavy duty liquid detergent formulations due to theiravailability from renewable resources and their biodegradability.Citrates can also be used in granular compositions, especially incombination with zeolite and/or layered silicate builders.Oxydisuccinates are also especially useful in such compositions andcombinations.

Also suitable in the detergent compositions of the present invention arethe 3,3-dicarboxy-4-oxa-1,6-hexanedioates and the related compoundsdisclosed in U.S. Pat. No. 4,566,984, Bush, issued Jan. 28, 1986. Usefulsuccinic acid builders include the C₅-C₂₀ alkyl and alkenyl succinicacids and salts thereof. A particularly preferred compound of this typeis dodecenylsuccinic acid. Specific examples of succinate buildersinclude: laurylsuccinate, myristylsuccinate, palmitylsuccinate,2-dodecenylsuccinate (preferred), 2-pentadecenylsuccinate, and the like.Laurylsuccinates are the preferred builders of this group, and aredescribed in European Patent Application 86200690.5/0,200,263, publishedNov. 5, 1986.

Other suitable polycarboxylates are disclosed in U.S. Pat. No.4,144,226, Crutchfield et al, issued Mar. 13, 1979 and in U.S. Pat. No.3,308,067, Diehl, issued Mar. 7, 1967. See also Diehl U.S. Pat. No.3,723,322.

Fatty acids, e.g., C₁₂-C₁₈ monocarboxylic acids, can also beincorporated into the compositions alone, or in combination with theaforesaid builders, especially citrate and/or the succinate builders, toprovide additional builder activity. Such use of fatty acids willgenerally result in a diminution of sudsing, which should be taken intoaccount by the formulator.

In situations where phosphorus-based builders can be used, andespecially in the formulation of bars used for hand-launderingoperations, the various alkali metal phosphates such as the well-knownsodium tripolyphosphates, sodium pyrophosphate and sodium orthophosphatecan be used. Phosphonate builders such asethane-1-hydroxy-1,1-diphosphonate and other known phosphonates (see,for example, U.S. Pat. Nos. 3,159,581; 3,213,030; 3,422,021; 3,400,148and 3,422,137) can also be used.

Bleach

The detergent compositions herein may optionally contain bleachingagents or bleaching compositions containing a bleaching agent and one ormore bleach activators. When present, bleaching agents will typically beat levels of from about 1% to about 30%, more typically from about 5% toabout 20%, of the detergent composition, especially for fabriclaundering. If present, the amount of bleach activators will typicallybe from about 0.1% to about 60%, more typically from about 0.5% to about40% of the bleaching composition comprising the bleachingagent-plus-bleach activator.

The bleaching agents used herein can be any of the bleaching agentsuseful for detergent compositions in textile cleaning, hard surfacecleaning, or other cleaning purposes that are now known or become known.These include oxygen bleaches as well as other bleaching agents.Perborate bleaches, e.g., sodiwn perborate (e.g., mono- ortetra-hydrate) can be used herein.

Another category of bleaching agent that can be used without restrictionencompasses percarboxylic acid bleaching agents and salts thereof.Suitable examples of this class of agents include magnesiummonoperoxyphthalate hexahydrate, the magnesium salt of metachloroperbenzoic acid, 4-nonylamino-4-oxoperoxybutyric acid anddiperoxydodecanedioic acid. Such bleaching agents are disclosed in U.S.Pat. No. 4,483,781, Hartman, issued Nov. 20, 1984, U.S. patentapplication No. 740,446, Burns et al, filed Jun. 3, 1985, EuropeanPatent Application 0,133,354, Banks et al, published Feb. 20, 1985, andU.S. Pat. No. 4,412,934, Chung et al, issued Nov. 1, 1983. Highlypreferred bleaching agents also include 6-nonylamino-6-oxoperoxycaproicacid as described in U.S. Pat. No. 4,634,551, issued Jan. 6, 1987 toBurns et al.

Peroxygen bleaching agents can also be used. Suitable peroxygenbleaching compounds include sodium carbonate peroxyhydrate andequivalent “percarbonate” bleaches, sodium pyrophosphate peroxyhydrate,urea peroxyhydrate, and sodium peroxide. Persulfate bleach (e.g., OXONE,manufactured commercially by DuPont) can also be used.

A preferred percarbonate bleach comprises dry particles having anaverage particle size in the range from about 500 micrometers to about1,000 micrometers, not more than about 10% by weight of said particlesbeing smaller than about 200 micrometers and not more than about 10% byweight of said particles being larger than about 1,250 micrometers.Optionally, the percarbonate can be coated with silicate, borate orwater-soluble surfactants. Percarbonate is available from variouscommercial sources such as FMC, Solvay and Tokai Denka.

Mixtures of bleaching agents can also be used.

Peroxygen bleaching agents, the perborates, the percarbonates, etc., arepreferably combined with bleach activators, which lead to the in situproduction in aqueous solution (i.e., during the washing process) of theperoxy acid corresponding to the bleach activator. Various nonlimitingexamples of activators are disclosed in U.S. Pat. No. 4,915,854, issuedApr. 10, 1990 to Mao et al, and U.S. Pat. No. 4,412,934. Thenonanoyloxybenzene sulfonate (NOBS) and tetraacetyl ethylene diamine(TAED) activators are typical, and mixtures thereof can also be used.See also U.S. Pat. No. 4,634,551 for other typical bleaches andactivators useful herein.

Highly preferred amido-derived bleach activators are those of theformulae:

R¹N(R⁵)C(O)R²C(O)L or R¹C(O)N(R⁵)R²C(O)L

wherein R¹ is an alkyl group containing from about 6 to about 12 carbonatoms, R² is an alkylene containing from 1 to about 6 carbon atoms, R⁵is H or alkyl, aryl, or alkaryl containing from about 1 to about 10carbon atoms, and L is any suitable leaving group. A leaving group isany group that is displaced from the bleach activator as a consequenceof the nucleophilic attack on the bleach activator by the perhydrolysisanion. A preferred leaving group is phenyl sulfonate.

Preferred examples of bleach activators of the above formulae include(6-octanamido-caproyl)oxybenzenesulfonate,(6-nonanamidocaproyl)oxybenzenesulfonate,(6-decanamido-caproyl)oxybenzenesulfonate, and mixtures thereof asdescribed in U.S. Pat. No. 4,634,551, incorporated herein by reference.

Another class of bleach activators comprises the benzoxazin-typeactivators disclosed by Hodge et al in U.S. Pat. No. 4,966,723, issuedOct. 30, 1990, incorporated herein by reference. A highly preferredactivator of the benzoxazin-type is:

Still another class of preferred bleach activators includes the acyllactam activators, especially acyl caprolactams and acyl valerolactamsof the formulae:

wherein R⁶ is H or an alkyl, aryl, alkoxyaryl, or alkaryl groupcontaining from 1 to about 12 carbon atoms. Highly preferred lactamactivators include benzoyl caprolactam, octanoyl caprolactam,3,5,5-trimethylhexanoyl caprolactam, nonanoyl caprolactam, decanoylcaprolactam, undecenoyl caprolactam, benzoyl valerolactam, octanoylvalerolactam, decanoyl valerolactam, undecenoyl valerolactam, nonanoylvalerolactam, 3,5,5-trimethylhexanoyl valerolactam and mixtures thereof.See also U.S. Pat. No. 4,545,784, issued to Sanderson, Oct. 8, 1985,incorporated herein by reference, which discloses acyl caprolactams,including benzoyl caprolactam, adsorbed into sodium perborate.

Bleaching agents other than oxygen bleaching agents are also known inthe art and can be utilized herein. One type of non-oxygen bleachingagent of particular interest includes photoactivated bleaching agentssuch as the sulfonated zinc and/or aluminum phthalocyanines. See U.S.Pat. No. 4,033,718, issued Jul. 5, 1977 to Holcombe et al. If used,detergent compositions will typically contain from about 0.025% to about1.25%, by weight, of such bleaches, especially sulfonate zincphthalocyanine.

If desired, the bleaching compounds can be catalyzed by means of amanganese compound. Such compounds are well known in the art andinclude, for example, the manganese-based catalysts disclosed in U.S.Pat. No. 5,246,621, U.S. Pat. No. 5,244,594; U.S. Pat. No. 5,194,416;U.S. Pat. No. 5,114,606; and European Pat. App. Pub. Nos. 549,271A1,549,272A1, 544,440A2, and 544,490A1; Preferred examples of thesecatalysts include Mn^(IV)₂(u-O)₃(1,4,7-trimethyl-1,4,7-triazacyclononane)2(PF6)₂, Mn^(III)₂(u-O)₁(u-OAc)₂(1,4,7-trimethyl-1,4,7-triazacyclononane)²⁻(ClO₄)₂,Mn^(IV) ₄(u-O)₆(1,4,7-triazacyclononane)4(ClO₄)₄, Mn^(III)Mn^(IV)₄(u-O)₁(u-OAc)²⁻(1,4,7-trimethyl-1,4,7-triazacyclononane)₂(ClO₄)₃,Mn^(IV)(1,4,7-trimethyl-1,4,7-triazacyclononane)-(OCH₃)₃(PF₆), andmixtures thereof. Other metal-based bleach catalysts include thosedisclosed in U.S. Pat. No. 4,430,243 and U.S. Pat. No. 5,114,611. Theuse of manganese with various complex ligands to enhance bleaching isalso reported in the following U.S. Pat. Nos. 4,728,455; 5,284,944;5,246,612; 5,256,779; 5,280,117; 5,274,147; 5,153,161; and 5,227,084.

As a practical matter, and not by way of limitation, the compositionsand processes herein can be adjusted to provide on the order of at leastone part per ten million of the active bleach catalyst species in theaqueous washing liquor, and will preferably provide from about 0.1 ppmto about 700 ppm, more preferably from about 1 ppm to about 500 ppm, ofthe catalyst species in the laundry liquor.

Enzymes

Enzymes can be included in the formulations herein for a wide variety offabric laundering purposes, including removal of protein-based,carbohydrate-based, or triglyceride-based stains, for example, and forthe prevention of refugee dye transfer, and for fabric restoration. Theenzymes to be incorporated include proteases, amylases, lipases,cellulases, and peroxidases, as well as mixtures thereof. Other types ofenzymes may also be included. They may be of any suitable origin, suchas vegetable, animal, bacterial, fungal and yeast origin. However, theirchoice is governed by several factors such as pH-activity and/orstability optima, thermostability, stability versus active detergents,builders and so on. In this respect bacterial or fungal enzymes arepreferred, such as bacterial amylases and proteases, and fungalcellulases.

Enzymes are normally incorporated at levels sufficient to provide up toabout 5 mg by weight, more typically about 0.01 mg to about 3 mg, ofactive enzyme per gram of the composition. Stated otherwise, thecompositions herein will typically comprise from about 0.001% to about5%, preferably 0.01%-1% by weight of a commercial enzyme preparation.Protease enzymes are usually present in such commercial preparations atlevels sufficient to provide from 0.005 to 0.1 Anson units (AU) ofactivity per gram of composition.

Suitable examples of proteases are the subtilisins which are obtainedfrom particular strains of B. subtilis and B. licheniforms. Anothersuitable protease is obtained from a strain of Bacillus, having maximumactivity throughout the pH range of 8-12, developed and sold by NovoIndustries A/S under the registered trade name ESPERASE. The preparationof this enzyme and analogous enzymes is described in British PatentSpecification No. 1,243,784 of Novo. Proteolytic enzymes suitable forremoving protein-based stains that are commercially available includethose sold under the tradenames ALCALASE and SAVINASE by Novo IndustriesA/S (Denmark) and MAXATASE by International Bio-Synthetics, Inc. (TheNetherlands). Other proteases include Protease A (see European PatentApplication 130,756, published Jan. 9, 1985) and Protease B (seeEuropean Patent Application Serial No. 87303761.8, filed Apr. 28, 1987,and European Patent Application 130,756, Bott et al, published Jan. 9,1985).

Amylases include, for example, α-amylases described in British PatentSpecification No. 1,296,839 (Novo), RAPIDASE, InternationalBio-Synthetics, Inc. and TERMAMYL, Novo Industries.

The cellulase usable in the present invention include both bacterial orfungal cellulase. Preferably, they will have a pH optimum of between 5and 9.5. Suitable cellulases are disclosed in U.S. Pat. No. 4,435,307,Barbesgoard et al, issued Mar. 6, 1984, which discloses fugal cellulaseproduced from Humicola insolens and Humicola strain DSM1800 or acellulase 212-producing fungus belonging to the genus Aeromonas, andcellulase extracted from the hepatopancreas of a marine mollusk(Dolabella Auricula Solander). suitable cellulases are also disclosed inGB-A-2.075.028; GB-A-2.095.275 and DE-OS-2.247.832. CAREZYME (Novo) isespecially useful.

Suitable lipase enzymes for detergent usage include those produced bymicroorganisms of the Pseudomonas group, such as Pseudomonas stutzeriATCC 19.154, as disclosed in British Patent 1,372,034. See also lipasesin Japanese Patent Application 53,20487, laid open to public inspectionon Feb. 24, 1978. This lipase is available from Amano Pharmaceutical Co.Ltd., Nagoya, Japan, under the trade name Lipase P “Amano,” hereinafterreferred to as “Amano-P.” Other commercial lipases include Amano-CES.lipases ex Chromobacter viscosum, e.g. Chromobacter viscosum var.lipolyticum NRRLB 3673, commercially available from Toyo Jozo Co.,Tagata, Japan; and further Chromobacter viscosum lipases from U.S.Biochemical Corp., U.S.A. and Disoynth Co., The Netherlands, and lipasesex Pseudomonas gladioli. The LIPOLASE enzyme derived from Humicolalanuginosa and commercially available from Novo (see also EPO 341,947)is a preferred lipase for use herein.

Peroxidase enzymes are used in combination with oxygen sources, e.g.,percarbonate, perborate, persulfate, hydrogen peroxide, etc. They areused for “solution bleaching,” i.e. to prevent transfer of dyes orpigments removed from substrates during wash operations to othersubstrates in the wash solution. Peroxidase enzymes are known in theart, and include, for example, horseradish peroxidase, ligninase, andhaloperoxidase such as chloro- and bromo-peroxidase.Peroxidase-containing detergent compositions are disclosed, for example,in PCT International Application WO 89/099813, published Oct. 19, 1989,by 0. Kirk, assigned to Novo Industries A/S.

A wide range of enzyme materials and means for their incorporation intosynthetic detergent compositions are also disclosed in U.S. Pat. No.3,553,139, issued Jan. 5, 1971 to McCarty et al. Enzymes are furtherdisclosed in U.S. Pat. No. 4,101,457, Place et al, issued Jul. 18, 1978,and in U.S. Pat. No. 4,507,219, Hughes, issued Mar. 26, 1985, both.Enzyme materials useful for liquid detergent formulations, and theirincorporation into such formulations, are disclosed in U.S. Pat. No.4,261,868, Hora et al, issued Apr. 14, 1981. Enzymes for use indetergents can be stabilized by various techniques. Enzyme stabilizationtechniques are disclosed and exemplified in U.S. Pat. No. 3,600,319,issued Aug. 17, 1971 to Gedge, et al, and European Patent ApplicationPublication No. 0 199 405, Application No. 86200586.5, published Oct.29, 1986, Venegas. Enzyme stabilization systems are also described, forexample, in U.S. Pat. No. 3,519,570.

Other components which are commonly used in detergent compositions andwhich may be incorpoated into the detergent tablets of the presentinvention include chelating agents, soil release agents, soilantiredeposition agents, dispersing agents, brighteners, sudssuppressors, fabric softeners, dye transfer inhibition agents andperfumes.

EXAMPLES

Comp. Comp. Ex. 1 Ex. 2 Ex. 3 Ex. 4 Anionic Agglomerates 24.48 19.5925.00 20.00 Nonionic Agglomerate 5.40 4.32 5.53 4.42 Bleach ActivatorAgglomerates 5.56 4.45 5.69 4.55 Zinc Phthalocyanine sulphonate 0.020.02 0.03 0.02 encapsulate Suds Suppressor 3.15 2.52 3.23 2.58 DriedZeolite 6.16 4.93 6.30 5.04 Layered Silicate 13.38 10.70 13.69 10.95 Dyetransfer Inhibitor Agglomerate 0.12 0.09 0.13 0.10 Perfume Encapsulates0.22 0.18 0.23 0.18 Nonionic Paste Spray-on 5.30 4.24 5.43 4.34Fluorescer 0.25 0.20 0.26 0.21 Sodium carbonate 4.57 3.66 4.68 3.74Sodium percarbonate 19.38 15.50 19.78 15.86 Sodium HEDP 0.77 0.62 0.790.63 Soil Release polymer 0.17 0.14 0.18 0.14 Perfume 0.32 0.25 0.330.26 Protease 0.85 0.68 0.86 0.69 Cellulase 0.24 0.19 0.25 0.20 Lipase0.21 0.16 0.21 0.17 Amylase 0.68 0.55 0.70 0.56 Adipic Acid 7.88 7.886.70 6.70 Effervescency Compact — 18.25 — 18.66 Disintegrant 0.88 0.88 —— NYMCEL ZSB-16 TOTAL 100.00 100.00 100.00 100.00

Anionic agglomerates comprise 38% anionic surfactant, 22% zeolite and40% carbonate.

Nonionic agglomerates comprise 26% nonionic surfactant, 48% zeolite and26% carbonate.

Bleach activator agglomerates comprise 81% TAED, 17% acrylic/maleiccopolymer (acid form) and 2% water.

Zinc Phthalocyanine sulphonate encapsulates are 10% active.

Suds suppressor comprises 11.5% silicone oil (ex Dow Corning), and 88.5%starch.

Layered silicate comprises 78% SKS-6, ex Hoechst, 22% citric acid.

Dye transfer inhibitor agglomerates comprise 21% PVNO/PVPVI, 61% zeoliteand 18% carbonate.

Perfume encapsulates comprise 50% perfume and 50% starch.

Nonionic paste spray-on comprises 67% C₁₂-C₁₅ AE5 (alcohol with anaverage of 5 ethoxy groups per molecule), 24% N-methyl glucose amide and9% water.

Effervescent compact comprises 54.5% sodium bicarbonate and 45.5% citricacid.

All the particulate materials of Example 1, except for the driedzeolite, were mixed together in a mixing drum to form a homogeneousparticulate mixture, during this mixing the spray-ons were carried out.After the spray-ons the dusting was carried out with the dried zeolite.

A first series of tablets were made the following way, about 37.5 g. ofthe mixture was introduced into a mould of circular shape with adiameter of 4.5 cm, and compressed with a force of 0.5 kN. or about 30Newton/cm², to give tablets of about 2.2 cm height and a density ofabout 1.1 g./cc. The tensile strength of the tablet was 3.5 kPa.

Adipic acid was heated in a thermostatic bath till 170° C. with gentlestirring until molten. The disintegrant, Nymcel ZSB-16®, was then addedwith continuous stirring to the adipic acid to form a suspension. Thetablets prepared as above were then dipped into the liquid to give thefinal coated tablet, this tablet had a total weight of 41.1 g, and atensile strength of 12.6 kPa.

A second series of tablets was made with a compaction force of 1 kN. orabout 65 N/cm² to give tablets of about 2.0 cm height, a density ofabout 1.2 g./cc, and a tensile strength of 9.0 kPa.

After coating with Adipic Acid the tablets had a weight of 41.2 g, andthe tensile strength was 21.2 kPa.

A third series of tablets was made with a compaction force of 1.5 kN. orabout 95N/cm² to give tablets of about 1.9 cm height, a density of about1.3 g./cc, and a tensile strength of 12.9 kPa. After coating with AdipicAcid the tablets had a weight of 41.1 g, and the tensile strength was31.5 kPa.

Example 2

Mixing according to the method described in Example 1, after the dustingthe effervescency granules were added to the mix drum, and a final mixwas made.

Tabletting and coating was carried out according to the method describedin Example 1

A first series of tablets was made with a Compaction Force of 1 kN. orabout 63 Newton/cm², to give tablets of about 2.2 cm height, a densityof about 1.1 gr./cc, and a tensile strength of 4.5 kPa.

After coating with Adipic acid the tablets had a weight of 41.1 g, andthe tensile strength was 14.4 kPa.

A second series of tablets was made with a compaction force of 1.5 kN.or about 95 N/cm² to give tablets of about 2.2 cm height, a density ofabout 1.2 gr./cc, and a tensile strength of 8.5 kPa.

After coating with Adipic Acid the tablets had a weight of 41.1 g, and atensile strength was 22.2 kPa.

A third series of tablets was made with a compaction force of 2.5 kN. orabout 160 N/cm² to give tablets of about 2.0 cm height, a density ofabout 1.2 g./cc, and a tensile strength of 15.7 kPa.

After coating with Adipic Acid the tablets had a weight of 41.1 g, andthe tensile strength increased to 31 kPa.

In Comparative Example 3, the process of example 1 was repeated butwithout the disintegrant. The final tensile strength of the three seriesof tablets was 6.5 kPa, 15.5 kPa and 19.5 kPa respectively.

In Comparative Example 4, the process of example 2 was repeated butwithout the disintegrant. The final tensile strength of the three seriesof tablets was 10.4 kPa, 14.5 kPa and 21.3 kPa respectively.

What is claimed is:
 1. A tablet comprising a core and a substantiallywater-insoluble coating, the core being formed by compressing aparticulate material, the particulate material comprising surfactant,detergent builder, and an effervescent wherein the coating comprises atleast a dicarboxylic acid and is applied from a melt having a meltingpoint of from 40° C. to about 200° C., and wherein the tablet furthercomprises a disintegrant, at least some of the disintegrant being in thecoating.
 2. A tablet according to claim 1 comprising a disintegrantselected from the group consisting of natural starch, modified starch,pregelatinized starch, sodium starch gluconate, croscarmylose Sodium,crospovidone, cellulose, carboxymethyl cellulose, algenic acid, sodiumalginate, silicone dioxide, clay, agar gum, guar gum, locust bean gum,karaya gum, pectin gum, tragacanth gum, polyvinylpyrrolidone, soypolysaccharides, ion exchange resins and mixtures thereof.
 3. A tabletaccording to claim 1 wherein the effervescent is a soluble acid sourceand an alkali metal carbonate.
 4. A process for making a tabletcomprising the steps of: (a) forming a core by compressing particulatematerial, the particulate material comprising surfactant, detergentbuilder and an effervescent; (b) applying a substantiallywater-insoluble coating material to the core, the coating materialcomprising at least a dicarboxylic acid in the form of a melt and havinga melting point of from 40° C. to about 200° C.; (c) allowing the moltencoating material to solidify; wherein the coating material comprises adisintegrant.
 5. A process for making a tablet comprising the steps of:(a) forming a core by compressing a particulate material, theparticulate material comprising surfactant, detergent builder and aneffervescent; (b) applying a substantially water-insoluble coatingmaterial to the core, the coating material comprising at least adicarboxylic acid being dissolved in a solvent; (c) allowing the solventto evaporate; wherein the coating material comprises a disintegrant.